Keysight U8903B, Руководство пользователя

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Audio Analyzer Measurement Functions 4
Keysight U8903B User’s Guide 225
Phase Measurement
Phase measurements are used to describe the positive or negative time offset in a periodic
waveform cycle (such as a sine waveform), measured from a reference waveform. The
reference is usually the same signal at a different point in the system, or a related signal in
a different channel of the system. Phase is expressed in degrees (°).
Phase shift varies with frequency, and therefore, it is common to make phase
measurements at several frequencies or to plot the phase response of a frequency sweep.
There are generally two types of phase measurements as follows.
– interchannel phase delay
– device phase response
To make an interchannel phase measurement, the signal level must be specified. Phase
measurements are generally not level-sensitive, as long as the signal is well above the
noise and below distortion.
For example, to test the interchannel phase delay of a stereo system, we inject a 1 Vrms,
1 kHz sine waveform using the same analog generator channel. The output of one channel
is connected to the analog analyzer channel 1 while the other is connected to channel 2.
Set the analog analyzer to measure phase. If channel 1 is set as the reference channel, the
channel 2 result is the interchannel phase delay.
A phase response measurement compares the phase of the output signal of a DUT to the
phase of the signal at its input. For example, a simple way to make this measurement is to
use the analog analyzer channel 1 to measure the input, and use the analog analyzer
channel 2 to measure the output.
The U8903B always uses channel 1 of the analog generator as the reference channel, while
the selected analog analyzer channel becomes the reference channel for interchannel
phase measurements.
Phase measurement function mode is applicable for the analog, digital, and Bluetooth
audio analyzer. The settings for phase measurement are displayed as shown in
Figure 4-45 , Figure 4-46 , and Figure 4-47 for both the analog, digital, and Bluetooth
analyzer respectively.
NOTE
Auto range will be disabled for phase measurement. Refer to “ Measurement Configuration
(Analog Analyzer) ” on page 238 to set the input voltage range.